1. Field of the Invention
The present invention relates to catalyst components for olefin polymerization, to the catalyst obtained from said components, and to the use of said catalysts in olefin polymerization. In particular, the present invention relates to catalyst components suitable for the stereospecific polymerization of olefins, including Ti, Mg, halogen and an electron donor compound selected from non-phthalate compounds having two or more functional radicals. Said catalyst components when used in the polymerization of olefins, and in particular of polypropylene, does not contain a phthalate.
2. Description of the Related Art
The use of Ziegler-Natta catalyst systems for olefin polymerization is well known in the art. For the polymerization of propylene, the widely used catalyst family belongs to the Ziegler-Natta category, generally comprising a solid catalyst component and a co-catalyst component, usually an organoaluminum compound. To improve the activity and sterospecificity of the catalyst system, certain electron donating compounds have been included and used (1) as an internal electron donor in the solid catalyst component and/or (2) as an external electron donor to be used in conjunction with the solid catalyst component and the co-catalyst component.
Common internal electron donor compounds, incorporated in the solid Ziegler-Natta catalyst components during preparation of such catalysts, include esters, ethers, ketones, amines, alcohols, phenols, phosphines and silanes. Of this group of compounds, phthalates, dibenzoic esters of 1,3-diol, diethers, and succinates have been most preferred. Examples of such internal electron donor compounds and their use as a component of the solid catalyst system are described in U.S. Pat. Nos. 4,107,414, 4,186,107, 4,226,963, 4,347,160, 4,382,019, 4,435,550, 4,465,782, 4,530,912, 4,532,313, 4,560,671, 4,657,882, 5,208,302, 5,902,765, 5,948,872, 6,121,483, 6,436,864, 6,770,586, 7,022,640, 7,049,377, 7,202,314, 7,208,435, 7,223,712, 7,351,778, 7,371,802, 7,491,781, 7,544,748, 7,674,741, 7,674,943, 7,888,437, 7,888,438, 7,964,678, 8,003,558 and 8,003,559, which are incorporated by reference herein.
This group of internal donors may be used in combination with an external donor, which is capable of good activity and yielding propylene polymers with high isotacticity and xylene or heptane insolubility endowed with an intermediate molecular weight distribution. Acceptable external electron donors include organic compounds containing O, Si, N, S, and P. Such compounds include organic acids, organic acid esters, organic acid anhydrides, ethers, ketones, alcohols, aldehydes, silanes, amides, amines, amine oxides, thiols, various phosphorus acid esters, amides etc. Preferred external donors are organosilicon compounds containing Si—O—C and/or Si—N—C bonds, having silicon as the central atom. Such compounds are described in U.S. Pat. Nos. 4,472,524, 4,473,660, 4,560,671, 4,581,342, 4,657,882, 5,106,807, 5,407,883, 5,684,173, 6,228,961, 6,362,124, 6,552,136, 6,689,849, 7,009,015, 7,244,794, 7,619,049 and 7,790,819, which are incorporated by reference herein.
Most commercial propylene polymerization catalysts currently use alkyl phthalates as an internal electron donor. However, certain environmental issues have been recently raised concerning the continued use of phthalates in human contact applications. As a result, the employment of a phthalate-free propylene polymerization catalyst is now necessary for the production of phthalate-free polypropylene to remedy these issues.
U.S. Pat. No. 7,491,781 in particular describes the use of an internal donor in a propylene polymerization catalyst component which does not contain a phthalate. However the resulted propylene polymerization catalyst has relatively poor hydrogen response and the polymer produced exhibits lower isotacticity than the catalyst containing a phthalate internal electron donor.
The polypropylene market also has an increasing demand for high melt flow rate (MFR) grade polypropylene to reduce cycle time and to achieve down-gauging while maintaining acceptable impact strength and stiffness. High MFR polypropylene is commonly achieved by adding peroxide to the polymer, but such obtained polypropylene usually has odor issues and the physical properties are sacrificed somehow. As such, production of reactor-grade high MFR polypropylene becomes necessary to avoid these issues.
As such, there is a continuous need for developing catalyst systems that can be used to produce polyolefins, particularly polypropylene, which does not contain a phthalate, and further offers the capability to produce reactor-grade polypropylene with acceptable isotacticity and high MFR.